Research Overview -
The research in Shikanov lab aims to develop means to restore ovarian reproductive and endocrine function in young women and girls with premature ovarian insufficiency (POI). POI is a common complication of anticancer treatments and it causes sterility and complications related to absent ovarian endocrine function such as premature osteopenia, muscle wasting, impaired cognitive development, and accelerated cardiovascular disease. The various projects in our laboratory address the critical need for safe fertility preservation options and contribute to our ability to extend fertility preservation to a population of young girls currently devoid of this option without the risk of cancer recurrence. We engineered a biomimetic environment for ovarian tissue with controlled physical and biological properties that promotes the survival and development of ovarian follicles. The biomimetic environment for in vivo applications, such as ovarian tissue implantation, promotes graft remodeling, revascularization and restoration of fertility and endocrine function. In vitro culture of the ovarian follicles in the biomimetic matrices mimics the physiological environment and leads to maturation of healthy eggs. We are also interested in molecular mechanisms involved in early stage development of ovarian follicles, design of novel 3D culture systems, engineering immunoisolating hydrogels for implantation of allogeneic tissues and creating oocytes from stem cells.
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Transcription factor activity during the development of early-stage ovarian follicles
Engineering an immuno-isolating hydrogel for restoring ovarian endocrine function
Design of 3D hydrogel system for ovarian follicle culture
The need for fertility preservation in females facing anticancer therapies provides an opportunity to use biomaterials in the field of reproductive biology. Presently, there are no in vitro technologies that can support the maturation of the immature female germ cell, the oocyte, into the developmental stage that can be used for in vitro fertilization (IVF) and the creation of offspring beyond the laboratory mouse. We synthesize and design biomaterials that can support healthy development of the immature ovarian follicle, while preserving its 3D architecture.
Development of the artificial ovary -
Ovarian tissue transplantation is another alternative to in vitro follicle culture for fertility preservation, yet it bears the risk of re-introduction of cancer cells and suffers from inconsistent graft longevity. We aim to engineer an artificial ovary from individually isolated human follicles through creative matrix design, incorporating supportive cells, ECM and other biological cues to ensure successful tissue remodeling after transplantation.
Transcription factor activity during the development of early-stage ovarian follicles -
Ovarian follicles are the functional units of the ovary and are responsible for a woman’s fertility and ovarian endocrine function. Currently, young women and prepubertal girls facing cancer diagnosis have limited options to preserve their fertility, with cryopreservation of ovarian tissue prior to chemotherapy the best available option. The challenge is that the vast majority of the follicles that survive the cryopreservation are early-stage primary and primordial follicles, and the subsequent success rate of their development and maturation in vitro is very low. These low success rates are attributed to the complex and poorly understood paracrine, autocrine and endocrine signaling between the cells in a follicle. Our goal is to identify the key signals and transcription factor activity during early stage follicle development that will result in a culture system design that maximizes follicle growth, health, and development. We have employed the TRACER assay developed by Dr. Lonnie Shea's research group to track transcription factor activity in real time and we have also employed microarray analysis to compare gene expression profiles in different culture systems
Engineering an immuno-isolating hydrogel for restoring ovarian endocrine function -
Premature ovarian insufficiency (POI) is a significant complication of cytotoxic treatments due to extreme ovarian sensitivity to chemotherapy and radiation. Currently available treatment for POI is hormone replacement therapy (HRT), which delivers unregulated, non-physiological levels of estrogen that interferes with growth in peripubertal girls, and predisposes them to cancer and thrombotic events. Implantation of donor ovarian tissue that responds to the circulating gonadotropins and secrets steroid hormones in response fills the existing gap, especially for the girls undergoing puberty. We designed a novel immuno-isolation device that protects the implanted tissue from rejection, allows diffusion of nutrients, oxygen and hormones, and accommodates structural and functional changes of growing follicles.
Reproductive Consequences of Steroid Administration -
The impact of long-term cross-sex hormone therapy on reproductive health in transgender men is largely unknown.National and international medical organizations recommend fertility preservation counseling prior to starting cross-sex hormone therapy, but these recommendations are based on an assumption of loss of fertility, not data. Data on histological changes in the human reproductive tract of transgender men (female-to-male or FTM) oncross-sex Testosterone (T) therapy are limited to observational studies at the time of surgery, mostly with short-term T exposure and inconsistent results. For both adult and peripubertal treatment strategies, it is unknown if the effects of T treatment on reproductive function can be completely reversed by cessation of T, partially reversed, or if fertility preservation is the best means for safeguarding future fertility potential. We have created a mouse model to mimic T therapy for the FTM gender transition.These mice manifest defects in ovarian and uterine architecture. Creation of a FTM mouse model provides a powerful tool to clarify the effects of T therapy on fertility, in a manner not possible in humans. The goal of projects to use FTM mouse model to investigate the effects of cross-sex T treatment on reproductive phenotype and function, and determine the reversibility of these effects following cessation of T.
Single Cell Atlas of the Human Ovary -
At birth, human ovaries contain around 1 million follicles, half of which degenerate before puberty, and only about 500 ovulate during a female’s reproductive lifespan. Follicle selection and integrated systemic and local signaling mechanisms remain largely unknown, and cannot be reproduced in vitro, presenting major challenges for treating disorders like infertility. Single cell RNA sequencing (scRNAseq) is a powerful tool for identifying rare cell populations, understanding the relationships between genes, and tracking cell lineage during differentiation or phenotypic change.Applying this technology to reproductive tissues specifically is complicated due to the shortage of human tissues for sequencing and the differences in the ovarian landscape between age groups—reproductive-aged tissues vary greatly from those of older individuals whose follicle reserves have been depleted. Our goal is to create a comprehensive transcriptional map of the cell types in the human ovary using scRNAseq, allowing us to decipher the transcriptional differences between follicular cells at different stages of development and identify stromal cells performing supportive functions to follicle development.